Intervertebral supports are known that provide a mutual support between vertebral discs that are overloaded and/or affected by various degenerative diseases. This reduces the loads acting on the discs. The use of intervertebral supports is a treatment alternative to the fusion of adjacent vertebrae, which consists of rigidly connecting to each other the vertebrae adjacent to a degenerated disc. This technique has the drawback of considerably reducing the mobility of the spine.
As shown in FIG. 1, an intervertebral support type is an interspinous support 10 is known that is configured to be arranged between the spinous apophysis 9a and 9b of two adjacent vertebrae 11a and 11b. Interspinous support 10 applies and receives forces to/from adjacent vertebrae 11a and 11b and reduces the load on the disc 16 that is located between them. For example, supports of this type are described in US2006/0271049 and in WO 2008/057838. Such supports provide a substantially immediate relief of pain to the patient, but are not suitable for stopping the degenerative breakdown of the disc and the vertebrae. In consequence, a segment of spine 11 that is affected by such a degenerative process is stabilized anomalously. Such condition is known as distability, and is caused by a shift of the instantaneous rotation axis 21 (FIG. 3). The relative movement of vertebrae 11a and 11b, i.e. the flexion-extension movement of spine 11, takes place about instantaneous rotation axis 21. In other words, the flexion-extension movement of the spine comprises a relative movement of adjacent vertebrae 11a and 11b that, over time, causes a local compression of intervertebral disc 16. This results into a damage of the pumping disc function, of the ligament system, and of the facet joints of vertebrae 11a and 11b. 
As shown in FIG. 2, interlaminar supports 20 are also known, which are described, for example, in WO 2004/084743. The interlaminar supports are arranged between the laminae 8a and 8b of adjacent vertebrae 11a and 11b. By the interlaminar supports, the two adjacent vertebrae 11a and 11b are spaced apart from each other following a substantially translational movement, which limits the local overloads that act on disc 16. However, such devices can retard the degenerative breakdown, but are not well suited for ultimately block it. Moreover, the interlaminar space 14 is very close to the spinal channel 15, where the nervous tissue is present. For this reason the positioning of interlaminar supports can be a critical matter.
Furthermore, the surgical implant of the intervertebral supports requires a considerably large access, in order to provide a suitable visibility and to allow handling the instruments required for suitably distracting the vertebrae, and in order to maintain such distraction.
WO01/41681 describes an intervertebral support assembly comprising a pair of bone allografts that are positioned between two adjacent vertebrae, towards the front portion of these vertebrae, and also comprising a pair of facet screws, each screw securing together two facets of the two vertebrae. Such vertebral support system, as well as all fusion systems, has the drawback of stiffening the two adjacent vertebrae with respect to each other, which severely reduces the mobility of the spine.
U.S. Pat. No. 6,113,637 describes a prosthesis for an intervertebral disc comprising a ball portion and a concave portion that is configured to engage with a second vertebra close to the first vertebra. The concavity of the concave portion includes a substantially flat surface. When the two portions engage with the respective vertebrae, they engage with each other enabling a relative rotation and translation movement of the vertebrae. Both portions comprise a flange for engaging a respective vertebra. The prosthesis has the drawback treating insufficiently an affected disc at the beginning of the degenerative breakdown, when a functional recovery of the disc is still possible.